Method of manufacturing mask blank and transfer mask

ABSTRACT

In a method of manufacturing a mask blank adapted to be formed with a resist pattern by electron beam writing and having a light-shielding film and an etching mask film of an inorganic-based material resistant to etching of the light-shielding film which are formed in this order on a transparent substrate, when forming the etching mask film, shielding is performed using a shielding plate so as to prevent the etching mask film from being formed at least at a side surface of the substrate.

This is a Divisional of U.S. application Ser. No. 12/264,424, filed Nov.4, 2008, which claims benefit of priority from Japanese patentapplication JP 2007-287272, filed on Nov. 5, 2007, the disclosure ofwhich are incorporated herein in their Entireties by reference.

TECHNICAL FIELD

This invention relates to methods of manufacturing a mask blank and atransfer mask for use in manufacturing semiconductor devices, displaydevices (display panels), or the like.

BACKGROUND ART

The miniaturization of semiconductor devices and the like isadvantageous in bringing about an improvement in performance andfunction (higher-speed operation, lower power consumption, etc.) and areduction in cost and thus has been accelerated more and more. Thelithography technique has been supporting this miniaturization andtransfer masks are a key technique along with exposure apparatuses andresist materials.

In recent years, use has been made of photomasks applied with theresolution enhancement technology (RET) such as the phase shifttechnique. A phase shift mask is a photomask that can improve theresolution of a transfer pattern using interference of light caused by aphase shifter.

Normally, the photolithography is performed by reduced projectionexposure in microprocessing of a semiconductor substrate and a patternof a transfer mask has a size about four times that of a pattern to beformed on the semiconductor substrate. However, in the photolithographyaccording to the semiconductor design rule of DRAM half-pitch (hp) 45 nmand onward, the size of a circuit pattern on a mask is smaller than awavelength of exposure light. Therefore, if a transfer mask formed witha transfer pattern according to the circuit pattern design is used tocarry out reduced projection exposure, a shape in conformity with thetransfer pattern cannot be transferred onto a resist film on asemiconductor substrate due to the influence of exposure lightinterference or the like.

Under these circumstances, as a mask employing the resolutionenhancement technology, use is made of an OPC mask or the like appliedwith a technique of correcting an optical proximity effect, whichdegrades the transfer characteristics, by performing optical proximityeffect correction (OPC) (Japanese Unexamined Patent ApplicationPublication (JP-A) No. H08-137089: Patent Document 1). For example, itis necessary to form on an OPC mask an OPC pattern (e.g. an assist baror a hammer head of a line width less than 100 nm) having a size half orless of that of a circuit pattern.

SUMMARY OF THE INVENTION

For forming a fine pattern according to the semiconductor design rule ofDRAM half-pitch (hp) 45 nm and onward, it is necessary to use high-NA(hyper-NA) exposure with a numerical aperture NA>1, for example,immersion exposure.

The immersion exposure is an exposure method that can improve theresolution by filling a liquid between a wafer and a lowermost lens ofan exposure apparatus so that the numerical aperture is increased by therefractive index of the liquid times as compared with that in the caseof air whose refractive index is 1. The numerical aperture is given byNA=n×sine, where 0 represents an angle formed between a light rayincident on the lowermost lens of the exposure apparatus at itsoutermost portion and the optical axis and n represents a refractiveindex of a medium between a wafer and the lowermost lens of the exposureapparatus.

However, it has been found that there is a problem in that the expectedCD accuracy cannot be obtained by employing the immersion exposure withNA>1 to form a fine pattern according to the semiconductor design ruleof DRAM half-pitch (hp) 45 nm (hereinafter referred to as “hp45nm”) andonward.

As one of its causes, there is an influence of mask blank charge-upwhich will be described hereinbelow.

Following the mask pattern miniaturization, the requirement for maskfabrication accuracy has also been getting stricter.

Particularly in the case of the hp45 nm and onward, following furthermask pattern miniaturization, the requirement for mask fabricationaccuracy will also be much stricter to make the mask fabricationdifficult. As one of factors that determine the mask fabricationaccuracy, the resist resolution is cited. In resist pattern formation inmask fabrication according to the hp45 nm and onward, electron beam (EB)writing capable of highly accurate writing is carried out becausepatterns are miniaturized and complicated. In the resist patternformation using the EB writing, a problem of charge-up is raised (seePatent Document 1). The problem is that, during EB writing of a resistpattern, a film underlying a resist is charged up and affects theresolution of the resist. In the EB writing, a measure such as reducingthe surface resistance of a mask blank is necessary for preventing thecharge-up.

The layer structure of a general mask blank is a laminate ofsubstrate/light-shielding film/resist and grounding from the mask blankset on a stage of an EB writing apparatus is normally performed at aside surface or a chamfered surface of the substrate (which of thesurfaces is used for grounding depends on the type of writingapparatus). For efficient grounding, the structure at end surfaces ofthe substrate (representing side surfaces and chamfered surfaces of thesubstrate; the same shall apply hereinafter) is such that the Cr film(light-shielding film) is formed down to the side surfaces of thesubstrate (see FIG. 1) and the resist at the side surfaces and thechamfered surfaces of the substrate is removed (see Japanese UnexaminedPatent Application Publication (JP-A) No. 2006-184353: Patent Document2).

On the other hand, the layer structure of a mask blank with an etchingmask (also called a hard mask) film is, for example, a laminate ofsubstrate/halftone film/Cr film/etching mask film/resist. If the etchingmask film covers the Cr film at side surfaces or chamfered surfaces ofthe substrate, since the surface resistance (sheet resistance) of theetching mask film is greater than that of the Cr film, the surface ofthe etching mask film is charged up during EB writing to increaseinfluence on the resolution of the resist, thus disturbing finepatterning. Therefore, the controllability of pattern processing isreduced. Accordingly, for suppressing the charge-up, during the EBwriting, of the etching mask film for use in forming a mask having afine pattern according to the hp45 nm and onward, there is required ameasure for efficiently grounding the mask blank on a stage of an EBwriting apparatus.

For efficiently grounding the mask blank on the stage of the EB writingapparatus, it may be considered to increase the exposed area of the Crfilm by preventing the etching mask film from being formed in agrounding region (side surfaces or chamfered surfaces of the substrate),i.e. by preventing the etching mask film from being formed at the endsurfaces (side surfaces or chamfered surfaces) of the substrate.

However, for example, if use is made of a shielding plate illustrated inFIG. 2 of Japanese Unexamined Patent Application Publication (JP-A) No.2002-90977 (Patent Document 3), it is necessary to cover the mainsurface of the substrate to some extent with the shielding plate inorder to prevent a film forming material from reaching the end surfaces(side surfaces or chamfered surfaces) of the substrate to form theetching mask film at those surfaces. Accordingly, the film formingregion of the etching mask film is narrowed. Then, there arises anotherproblem that since there is a region formed with no etching mask film atthe peripheral portion of the main surface, a pattern cannot be formedin such a region. Specifically, as illustrated in FIG. 2, an alignmentmark 5 for use in setting a mask in a wafer exposure apparatus (stepper)is formed at the peripheral portion of the main surface of a substrate1. There is a problem that if an etching mask film 3 is not formed atthe peripheral portion of the main surface of the substrate 1, a lackoccurs in the alignment mark 5 formed by a light-shielding film 2 and,if this lack in alignment mark pattern is significant, the mask cannotbe set in the exposure apparatus. For preventing the occurrence of thelack in the alignment mark 5, it is necessary to further extend the filmforming region of the etching mask film 3. However, there is a problemthat if attempting to extend the film forming region of the etching maskfilm 3 in consideration of the position of the alignment mark 5 on themask while using the shielding plate illustrated in FIG. 2 of PatentDocument 3, the etching mask film 3 is formed at end surfaces of thesubstrate 1.

This invention has been made in view of the above problems and has anobject to provide a mask blank manufacturing method and a mask blank,that can prevent an etching mask film from being formed at end surfacesof a substrate so as to prevent the occurrence of charge-up and,further, that can extend a film forming region of the etching mask filmso as to prevent the occurrence of a lack in an alignment mark.

This invention has the following structures.

(Structure 1) A method of manufacturing a mask blank adapted to beformed with a resist pattern by electron beam writing and having alight-shielding film and an etching mask film of an inorganic-basedmaterial resistant to etching of the light-shielding film which areformed in this order on a transparent substrate,

wherein, when forming the etching mask film, shielding is performedusing a shielding plate so as to prevent the etching mask film frombeing formed at least at a side surface of the substrate.

Herein, it is noted that Structure 1 may correspond to features recitedin claim 1. According to the invention of Structure 1, when forming theetching mask film, the shielding is performed using the shielding plateso as to prevent the etching mask film from being formed at least at theside surface of the substrate. Therefore, there is obtained the maskblank in which the etching mask film is not present at least at the sidesurface of the substrate. With this mask blank, since thelight-shielding film is exposed at the side surface of the substrate,the mask blank can be efficiently grounded at the side surface of thesubstrate during the EB writing so that it is possible to preventcharge-up of the mask blank and thus to reduce the influence on theresolution of a resist.

(Structure 4) A mask blank adapted to be formed with a resist pattern byelectron beam writing and having a light-shielding film and an etchingmask film of an inorganic-based material resistant to etching of thelight-shielding film which are formed in this order on a transparentsubstrate,

wherein the light-shielding film is made of a material being conductiveso that the light-shielding film is not charged up during patterning byelectron beam writing, and the etching mask film is not present at leastat a side surface of the substrate.

Herein, it is noted that Structure 4 may correspond to features recitedin claim 4. According to the invention of Structure 4, there is obtainedthe mask blank in which the etching mask film is not present at least atthe side surface of the substrate. With this mask blank, since thelight-shielding film is exposed at the side surface of the substrate,the mask blank can be efficiently grounded at the side surface of thesubstrate during the EB writing so that it is possible to preventcharge-up of the mask blank and thus to reduce the influence on theresolution of a resist.

(Structure 2) In the above-mentioned Structures, a film forming regionof the etching mask film is at least inside the side surface of thesubstrate and outside an alignment mark so as to prevent occurrence of alack in the alignment mark.

Herein, it is noted that Structure 2 may correspond to features recitedin claim 2. With this structure, in addition to the operation and effectof the above-mentioned Structures, it is possible to extend the filmforming region of the etching mask film without forming the etching maskfilm at the end surface (side surface or chamfered surface) of thesubstrate. Therefore, in addition to preventing charge-up of the etchingmask film, it is also possible to securely form an alignment mark sincethe film forming region of the etching mask film can be extended.

In this invention, when a portion for grounding the mask blank on astage of an EB writing apparatus is a chamfered surface of thesubstrate, it is preferable to extend the film forming region of theetching mask film to the position of a line B′ parallel to an outermostside B of a main surface of the substrate 1 and offset inward from theside B by a predetermined distance (see FIG. 1). It is preferable thatthe distance between B and B′ be 2 mm or less for securely forming thealignment mark.

In this invention, when a portion for grounding the mask blank on astage of an EB writing apparatus is a side surface of the substrate, itis possible to extend the film forming region of the etching mask filmto the position of a line A′ parallel to a side surface A of thesubstrate 1 and offset inward from the side surface A by a predetermineddistance (see FIG. 1). It is preferable that the distance between A andA′ be 1 mm or less for securely forming the alignment mark.

In this invention, as illustrated in FIG. 1, it is most preferable thatthe film forming region of the etching mask film be extended to theoutermost side B of the main surface (i.e. an end B of the main surfaceor an intersection line B between the main surface and the chamferedsurface) of the substrate 1. This mode is preferable because it ispossible to form the alignment mark more securely as compared with thecase where the film forming region of the etching mask film is narrowerthan this mode. According to this mode, since the etching mask film isnot formed at either the side surface or the chamfered surface of thesubstrate, grounding can be performed at either of the side surface andthe chamfered surface of the substrate and thus it is possible toprovide the mask blank that is applicable to writing apparatusesregardless of the type of grounding thereof.

(Structure 3) In the above-mentioned Structures, the shielding plate ismade of an elastic material and is brought into contact with or intoclose vicinity to the substrate so that the shielding is performed.

Herein, it is noted that Structure 3 may correspond to features recitedin claim 3. With this structure, it is possible to extend the filmforming region of the etching mask film without forming the etching maskfilm at the end surface (side surface or chamfered surface) of thesubstrate.

In this invention, as the elastic material, a rubber material, afluorine-based resin (e.g. Teflon (registered trademark)), or the likecan be suitably used.

In this invention, for example, the shielding plate is a sheet(plate-like member) made of a rubber material and having an opening withthe same area as that of the main surface of the substrate and ispressed against the substrate so as to be brought into contact with orinto adhesion to the substrate, thereby achieving the shielding. Theopening of the shielding plate may be increased or reduced in size orchanged in shape. Further, it is possible to perform the shielding bybringing the shielding plate into close vicinity to the substrate with aslight gap therebetween.

In this invention, it may be configured that, for example, the shieldingplate is brought into contact with the side surface and the chamferedsurface of the substrate or into close vicinity to them with a slightgap therebetween to thereby shield those portions while the end B of themain surface is not shielded by the shielding plate (see FIG. 3).

(Structure 5) A method of manufacturing a transfer mask, comprising:

forming an electron beam writing resist layer on the etching mask filmin the above-mentioned mask blank;

applying electron beam writing and development to the electron beamwriting resist layer to form the resist pattern;

etching the etching mask film using the resist pattern as a mask totransfer the resist pattern onto the etching mask film, thereby forminga pattern of the etching mask film; and

etching the light-shielding film using the resist pattern and thepattern of the etching mask film as a mask or using the pattern of theetching mask film as a mask to transfer the pattern onto thelight-shielding film, thereby forming a pattern of the light-shieldingfilm.

Herein, it is noted that Structure 5 may correspond to features recitedin claim 5. According to the invention of Structure 5, since use is madeof the mask blank in which the etching mask film is not present at theside surface or the chamfered surface of the substrate, i.e. the maskblank in which the light-shielding film is exposed at the side surfaceor the chamfered surface of the substrate, the mask blank can beefficiently grounded at the side surface or the chamfered surface of thesubstrate during the EB writing so that it is possible to preventcharge-up of the mask blank and thus to reduce the influence on theresolution of the resist.

According to this invention, by performing the shielding so as toprevent the etching mask film from being formed at the side surface orthe chamfered surface of the substrate, the light-shielding film isexposed there. Consequently, the mask blank can be efficiently groundedduring the EB writing so that it is possible to prevent charge-up of themask blank and thus to reduce the influence on the resolution of theresist. In addition thereto, it is possible to extend the film formingregion of the etching mask film without forming the etching mask film atthe end surface of the substrate. Therefore, in addition to preventingcharge-up of the etching mask film, it is also possible to securely formthe alignment mark since the film forming region of the etching maskfilm can be extended.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial sectional view illustrating one example of a maskblank according to this invention;

FIG. 2 is a partial plan view for explaining a problem of a lack in analignment mark; and

FIG. 3 is a partial sectional view for explaining one mode of ashielding plate according to this invention.

DESCRIPTION OF THE EXEMPLARY EMBODIMENT

Hereinbelow, an embodiment according to this invention will be describedwith reference to the drawings.

FIG. 1 illustrates one example of a mask blank according to theembodiment of this invention. In this example, the mask blank is abinary mask blank and comprises a transparent substrate 1, alight-shielding film 2, an etching mask film 3, and a resist film 4 inthis order.

As the light-shielding film 2, use can be made of a metal filmcontaining a metal. As the metal film containing the metal, there iscited a film made of chromium, tantalum, molybdenum, titanium, hafnium,tungsten, any of alloys containing those elements, or any of materialscontaining those elements or those alloys (e.g. a film containing atleast one of oxygen, nitrogen, silicon, and carbon in addition to any ofthe materials containing those elements or those alloys).

As the light-shielding film 2, use can be made of, for example, a filmmade of chromium alone or a material containing chromium and at leastone element selected from oxygen, nitrogen, carbon, and hydrogen(Cr-containing material). The light-shielding film 2 may have a filmstructure composed of a single layer or a plurality of layers made ofthe above film material. With different compositions, thelight-shielding film 2 may have a film structure in which a plurality oflayers are formed stepwise or a film structure in which the compositioncontinuously changes.

The specific light-shielding film 2 is a laminated film composed of alight-shielding layer in the form of a chromium nitride film (CrN film)and a chromium carbonitride film (CrCN film) and an antireflection layerin the form of a film containing chromium, oxygen, and nitrogen (CrONfilm). The chromium nitride film is a layer mainly containing chromiumnitride (CrN) and has a thickness of, for example, 10 to 20 nm. Thechromium carbonitride film is a layer mainly containing chromiumcarbonitride (CrCN) and has a thickness of, for example, 25 to 60 nm.The film containing chromium, oxygen, and nitrogen (CrON film) has athickness of, for example, 15 to 30 nm.

In this invention, as the light-shielding film 2, it is preferable touse a material being conductive so that it is not charged up duringpatterning by electron beam writing.

In this invention, as illustrated in FIG. 1, the light-shielding film 2is formed from a main surface of the substrate 1 down to side surfacesor chamfered surfaces of the substrate 1.

As the etching mask film 3, use can be made of, for example, asilicon-containing film containing silicon. As the silicon-containingfilm, there is cited a silicon film, a metal silicide film containingsilicon and a metal such as chromium, tantalum, molybdenum, titanium,hafnium, or tungsten, or a film containing at least one of oxygen,nitrogen, and carbon in the silicon film or the metal silicide film. Asthe etching mask film 3, use can be made of, for example, a film mainlycontaining a transition metal silicide oxide, a transition metalsilicide nitride, a transition metal silicide oxynitride, a transitionmetal silicide oxycarbide, a transition metal silicide nitride carbide,or a transition metal silicide oxynitride carbide. As the etching maskfilm 3, use can be made of, for example, a molybdenum-based (MoSiON,MoSiN, MoSiO, or the like) film, a tungsten-based (WSiON, WSiN, WSiO, orthe like) film, a silicon-based (SiN, SiON, or the like) film, or achromium-based (CrO, CrF, or the like) film. For example, the etchingmask film 3 is preferably made of MoSiN or SiON.

In this invention, as illustrated in FIG. 1, it is most preferable thatthe film forming region of the etching mask film 3 be extended tooutermost sides B of the main surface (i.e. ends B of the main surfaceor intersection lines B between the main surface and the chamferedsurfaces) of the substrate 1.

In this invention, a photomask blank, a phase shift mask blank, areflective mask blank, and an in-print transfer plate substrate are alsoincluded in mask blanks. Further, a mask blank with a resist film and amask blank before formation of a resist film are included in maskblanks. A phase shift mask blank may have a structure in which alight-shielding film of a chromium-based material or the like is formedon a halftone film. A reflective mask blank may have a structure inwhich an absorbent film of a tantalum-based material or a chromium-basedmaterial to be a transfer pattern is formed on a multilayer reflectivefilm or a buffer layer provided on a multilayer reflective film. Anin-print transfer plate may have a structure in which a thin film fortransfer pattern formation of a chromium-based material or the like isformed on a base member that serves as a transfer plate.

In this invention, a mask blank, in which a thin film for transferpattern formation and an etching mask film of an inorganic-basedmaterial resistant to etching of the thin film for transfer patternformation are formed in this order on a transparent substrate, isincluded in mask blanks. In this case, the thin film for transferpattern formation is made of a material being conductive so that it isnot charged up during patterning by electron beam writing. The contentsdescribed above are also applicable by replacing a “light-shieldingfilm” with a “thin film for transfer pattern formation”.

In this invention, a photomask, a phase shift mask, a reflective mask,and an in-print transfer plate are included in masks. A reticle isincluded in masks. A phase shift mask may have a structure in which aphase shifter is formed by etching a substrate.

In this invention, as a substrate, there is cited a synthetic quartzsubstrate, a soda-lime glass substrate, an alkali-free glass substrate,a low thermal expansion glass substrate, or the like.

In this invention, it is preferable to use a dry etching gas such as achlorine-based gas or a mixed gas containing a chlorine-based gas and anoxygen gas in dry etching of a chromium-based thin film. This isbecause, by performing dry etching of a chromium-based thin film, madeof a material containing chromium and an element such as oxygen ornitrogen, using the above dry etching gas, it is possible to increasethe dry etching rate and thus to shorten the dry etching time to therebyform a light-shielding film pattern with an excellent sectional shape.As the chlorine-based gas for use as or in the dry etching gas, there iscited, for example, Cl₂, SiCl₄, HCl, CCl₄, or CHCl₃.

In this invention, in dry etching of a silicon-containing filmcontaining silicon or a metal silicide-based thin film, use can be madeof, for example, a fluorine-based gas such as SF₆, CF₄, C₂F₆, or CHF₃,or a mixed gas thereof with He, H₂, N₂, Ar, O₂H₄, or O₂, or achlorine-based gas such as Cl₂ or CH₂Cl₂, or a mixed gas thereof withHe, H₂, N₂, Ar, or O₂H₄.

In this invention, as a phase shift film, use can be made of, forexample, a silicon-containing film containing silicon. As thesilicon-containing film, there is cited a silicon film, a metal silicidefilm containing silicon and a metal such as chromium, tantalum,molybdenum, titanium, hafnium, or tungsten, or a film containing atleast one of oxygen, nitrogen, and carbon in the silicon film or themetal silicide film. As a phase shift film, use can be made of, forexample, a film mainly containing a transition metal silicide oxide, atransition metal silicide nitride, a transition metal silicideoxynitride, a transition metal silicide oxycarbide, a transition metalsilicide nitride carbide, or a transition metal silicide oxynitridecarbide. As a phase shift film, use can be made of, for example, amolybdenum-based (MoSiON, MoSiN, MoSiO, or the like) halftone film, atungsten-based (WSiON, WSiN, WSiO, or the like) halftone film, asilicon-based (SiN, SiON, or the like) halftone film, or achromium-based (CrO, CrF, or the like) halftone film.

As a phase shift film, use can be made of, for example, a halftone filmcomposed of two layers, i.e. a phase adjusting layer for mainlycontrolling the phase of exposure light and a transmittance adjustinglayer for mainly controlling the transmittance of exposure light.

Hereinbelow, Examples of this invention and Comparative Examples thereofwill be shown.

Example 1 and Comparative Examples 1 and 2 Manufacture of Mask Blank

Referring to FIG. 2, a description will be given of a photomaskmanufacturing method according to Example 1 of this invention.

At first, a substrate made of quartz was mirror-polished and thencleaned, thereby obtaining a light-transmissive substrate 1 of 6inches×6 inches×0.25 inches.

Then, using an in-line sputtering apparatus where a plurality ofchromium (Cr) targets were disposed in the same chamber, alight-shielding chromium film 2 composed of a CrN film, a CrC film, anda CrON film was formed on the light-transmissive substrate 1.Specifically, at first, reactive sputtering was carried out in a mixedgas atmosphere of argon (Ar) and nitrogen (N₂) (Ar:N₂=72:28 [vol %];pressure: 0.3 [Pa]), thereby forming the CrN film having a thickness of15 [nm]. Subsequently, reactive sputtering was carried out in a mixedgas atmosphere of argon (Ar) and methane (CH₄) (Ar:CH₄=96.5:3.5 [vol %];pressure: 0.3 [Pa]), thereby forming the CrC film having a thickness of20 [nm] on the CrN film. Subsequently, reactive sputtering was carriedout in a mixed gas atmosphere of argon (Ar) and nitrogen monoxide (NO)(Ar:NO=87.5:12.5 [vol %]; pressure: 0.3 [Pa]), thereby forming the CrONfilm having a thickness of 20 [nm] on the CrC film. The above CrN film,CrC film, and CrON film were continuously formed using the in-linesputtering apparatus and thus the light-shielding chromium film 2containing these CrN, CrC, and CrON was configured such that thesecomponents continuously changed in a thickness direction thereof.

Then, using a mixed target of molybdenum (Mo) and silicon (Si)(Mo:Si=1:9 [at %]), reactive sputtering was carried out in a mixed gasatmosphere of argon (Ar) and nitrogen (N₂) (Ar:N₂=10:90 [vol %];pressure: 0.3 [Pa]), thereby forming a MoSiN-based inorganic-basedetching mask film 3 having a thickness of 20 [nm] on the light-shieldingchromium film 2.

In this event, in Example 1, the etching mask film 3 was formed bytightly pressing a sheet (plate-like member), made of a silicon rubbermaterial and having an opening with the same area as that of the mainsurface of the substrate 1, against the substrate 1 to shield the sidesurfaces and the chamfered surfaces of the substrate 1. This made itpossible to extend the film forming region of the etching mask film 3 tothe outermost sides B of the main surface of the substrate 1 asillustrated in FIG. 1.

On the other hand, in each of Comparative Examples 1 and 2, the etchingmask film 3 was formed using the shielding plate illustrated in FIG. 2of Patent Document 3. However, when attempting to extend the filmforming region of the etching mask film in consideration of the positionof an alignment mark on a mask, the etching mask film was formed at theside surfaces or the chamfered surfaces of the substrate (ComparativeExample 1). Further, when attempting not to form the etching mask filmat the side surfaces or the chamfered surfaces of the substrate, thefilm forming region of the etching mask film was narrowed (e.g. to theinside of B′) (Comparative Example 2).

Then, a chemically amplified positive resist 4 for electron beam writing(exposure) (FEP171: manufactured by FUJIFILM Electronic Materials Co.,Ltd.) was spin-coated to a thickness of 200 [nm] on the inorganic-basedetching mask film 3 (see FIG. 1).

In this manner, there was prepared a mask blank in which thelight-shielding chromium film 2 of the Cr-based materials, theinorganic-based etching mask film 3 of the MoSiN-based material, and theresist 4 were formed in this order on the light-transmissive substrate1.

The sheet resistance was measured for the sample at the stage where thelight-shielding chromium film 2 was formed, and it was 120Ω/square.

Further, the sheet resistance was measured for the sample at the stagewhere the etching mask film 3 was formed, and it was 170Ω/square.

(Manufacture of Mask)

Then, the resist 4 was subjected to electron beam writing by the use ofJBX9000 manufactured by JEOL Ltd. and then was developed, therebyforming a resist pattern. In this event, in each of Example 1 andComparative Examples 1 and 2, the mask blank was grounded at its sidesurface or chamfered surface on a stage of an EB writing apparatus.

Then, using the resist pattern as a mask, dry etching mainly withionicity was carried out at a pressure of 5 [mmTorr] using a mixed gasof SF₆ and He to etch the inorganic-based etching mask film 3, therebyforming an inorganic-based etching mask pattern.

Then, the resist pattern was removed. Thereafter, using only theinorganic-based etching mask pattern as a mask, dry etching mainly withradicals where ionicity was increased as much as possible (=ionicity wasincreased to a level where ions and radicals became approximately equalto each other) was carried out at a pressure of 3 mmTorr using a mixedgas of Cl₂ and O₂ to etch the light-shielding chromium film 2, therebyforming a light-shielding chromium pattern.

Then, the inorganic-based etching mask pattern was stripped and thencleaning was carried out, thereby obtaining a photomask.

(Evaluation)

The masks thus obtained were evaluated.

As a result, with respect to the mask according to Example 1, nocharge-up was observed in the mask manufacturing process and there wasobserved no reduction in CD accuracy considered to be caused by thecharge-up. Accordingly, it was confirmed that it would be possible toaccurately process a fine pattern of a hp45 nm mask. Further, analignment mark (see FIG. 2) was securely formed with no lack.

With respect to the mask according to Comparative Example 1, charge-upwas observed in the mask manufacturing process and there was observed areduction in CD accuracy considered to be caused by the charge-up.

With respect to the mask according to Comparative Example 2, a lackoccurred in an alignment mark (see FIG. 2) and thus the alignment markfailed in function.

Example 2

Example 2 was the same as Example 1 except that an inorganic-basedetching mask film 3 was made of SiON instead of MoSiN.

The results of the evaluation were the same as those of Example 1.

While this invention has been described based on the embodiment, thetechnical scope of this invention is not limited thereto. It is readilyunderstood by a person skilled in the art that various modifications orimprovements can be added to the foregoing embodiment. It is apparentfrom the description of the claims that the modes added with thosemodifications or improvements can also be included in the technicalscope of this invention.

1. A mask blank for application of a resist pattern by electron beamwriting, comprising: a transparent substrate; and a lamination film,including at least a first film and a second film, the lamination filmbeing formed on a main surface; wherein the first film is formed on achamfered surface of the transparent substrate and is made of a firstfilm material, which has a first conductivity so that the first film isnot charged up during patterning by the electron beam writing, andwherein the second film is not formed on the chamfered surface of thetransparent substrate and is made of a second film material, which has asecond conductivity so that the second film may be charged up during thepatterning by the electron beam writing.
 2. The mask blank according toclaim 1, wherein the first film is made of any one of (1) a firstmaterial made of a selected element, which is selected from the groupconsisting of chromium, tantalum, molybdenum, titanium, hafnium andtungsten, (2) a second material made of alloy containing the selectedelement, and (3) a third material containing at least one of oxygen,nitrogen, silicon, and carbon in combination with the first material orthe second material.
 3. The mask blank according to claim 1, wherein thefirst film is made of any one of (1) a material made of chromium aloneand (2) a material containing chromium and at least one element selectedfrom oxygen, nitrogen, carbon and hydrogen.
 4. The mask blank accordingto claim 1, wherein the second film comprises any one of (1) a siliconfilm, (2) a metal silicide film containing silicon and at least one ofchromium, tantalum, molybdenum, titanium, hafnium and tungsten, and (3)a film containing at least one of oxygen, nitrogen and carbon in one ofthe silicon film and the metal silicide film.
 5. The mask blankaccording to claim 1, wherein the second film is made of a materialselected from the group consisting of MoSiON, MoSiN, MoSiO, WSiON, WSiN,WSiO, SiN, SiON, CrO and CrF.
 6. The mask blank according to claim 1,wherein the second film is at least inside a side surface of thesubstrate and outside an alignment mark.
 7. The mask blank according toclaim 1, wherein the first film and the second film are formed in anorder on the transparent substrate whereby the second film is formedover the first film.
 8. The mask blank according to claim 1, wherein thesecond conductivity of the second film material is lower than the firstconductivity of the first film material.
 9. The mask blank according toclaim 1, wherein the first film material has a first surface resistancecorresponding to the first conductivity, the second film material has asecond surface resistance corresponding to the second conductivity, andthe second resistance of the second film material is greater than thefirst resistance of the first film material.
 10. The mask blankaccording to claim 1, further comprising: a resist film formed on thelamination film, the resist film being applied to the electron beamwriting.
 11. A method of manufacturing a transfer mask, comprising:providing a mask blank made according to claim 10, and forming atransfer mask from said mask blank.
 12. A mask blank, which is adaptedto be formed with a resist pattern by electron beam writing, comprising:a transparent substrate; and a lamination film, including at least afirst film and a second film, the lamination film being formed on a mainsurface; wherein the first film is formed on a side surface and achamfered surface of the transparent substrate and is made of a firstfilm material which has a first conductivity so that the first film isnot charged up during patterning by the electron beam writing, andwherein the second film is not formed on the side surface of thetransparent substrate and is made of a second film material which has asecond conductivity so that the second film may be charged up during thepatterning by the electron beam writing.
 13. The mask blank according toclaim 12, wherein the first film is made of any one of (1) a firstmaterial made of a selected element, which is selected from the groupconsisting of chromium, tantalum, molybdenum, titanium, hafnium andtungsten, (2) a second material made of alloy containing the selectedelement, and (3) a third material containing at least one of oxygen,nitrogen, silicon, and carbon in combination with the first material orthe second material.
 14. The mask blank according to claim 12, whereinthe first film is made of any one of (1) a material made of chromiumalone and (2) a material containing chromium and at least one elementselected from oxygen, nitrogen, carbon and hydrogen.
 15. The mask blankaccording to claim 12, wherein the second film comprises any one of (1)a silicon film, (2) a metal silicide film containing silicon andchromium, tantalum, molybdenum, titanium, hafnium or tungsten, and (3) afilm containing at least one of oxygen, nitrogen and carbon in thesilicon film or the metal silicide film.
 16. The mask blank according toclaim 12, wherein the second film is made of a material selected fromthe group consisting of MoSiON, MoSiN, MoSiO, WSiON, WSiN, WSiO, SiN,SiON, CrO and CrF.
 17. The mask blank according to claim 12, wherein thesecond film is at least inside the side surface of the substrate andoutside an alignment mark so as to prevent occurrence of a lack in thealignment mark.
 18. The mask blank according to claim 12, wherein thefirst film and the second film are formed in this order on thetransparent substrate.
 19. The mask blank according to claim 12, whereinthe second conductivity of the second film material is lower than thefirst conductivity of the first film material.
 20. The mask blankaccording to claim 12, wherein the first film material has a firstsurface resistance corresponding to the first conductivity, the secondfilm material has a second surface resistance corresponding to thesecond conductivity, and the second resistance of the second filmmaterial is greater than the first resistance of the first filmmaterial.
 21. The mask blank according to claim 12, further comprising:a resist film formed on the lamination film, the resist film beingapplied to the electron beam writing.
 22. A method of manufacturing atransfer mask, wherein the transfer mask is produced by using the maskblank according to claim
 21. 23. The method of manufacturing mask blankaccording to claim 11, wherein the providing step includes grounding ofsaid first film.
 24. The method of manufacturing a mask blank accordingto claim 23, wherein the grounding is by contact of a ground with saidchamfered surface.
 25. A method of manufacturing a transfer mask,comprising: providing a mask blank made according to claim 12, andforming a transfer mask from said mask blank.
 26. The method ofmanufacturing mask blank according to claim 25, wherein the providingstep includes grounding of said first film.
 27. The method ofmanufacturing a mask blank according to claim 26, wherein the groundingis by contact of a ground with said chamfered surface.